In motor vehicle technology, components such as transmission systems, engine systems or brake systems are increasingly being primarily controlled electronically. This involves a development toward integrated mechatronic control systems, that is to say for integrated control electronics and the associated electronic components such as sensors or valves into the transmission, the engine or the brake system. Therefore, control devices generally have a large number of electronic components which are connected to other components outside the control device. In the case of “on-site electronics systems” of this kind, these control systems are no longer accommodated in a separate protected electronics compartment and therefore have to withstand corresponding environmental influences and mechanical, thermal and chemical loads. For this purpose, they are normally inserted into special housings.
An electronic connection from the inside of the housing to the outside of the housing is needed in order to allow a reliable connection to components which are positioned outside the housing.
The circuit carriers for control systems of this kind are generally constructed, introduced into a housing and this housing is then closed. An example of this is described in DE 10 2007 038 331 A1. However, this housing structure does not guarantee absolute leak-tightness against diffusion and/or permeation. Over the course of time, harmful gases can reach the circuit carrier and lead to corrosion of metal.
In an alternative design, the entire circuit structure for protecting the circuit carrier is completely encapsulated with a molding composition. An example of this is described in DE 10 2011 082 537 A1. The process management of the molding process has to be precisely complied with in this case. Otherwise, if unhoused electronic components, so-called bare dies, which are electrically connected to the circuit carrier by gold wire connections are used, so-called bonding wire drifting phenomena may occur. Furthermore, the coefficient of thermal expansion of the molding material has to be precisely matched to the entire structure comprising carrier substrate, components etc. Otherwise gaps may form between the molding composition and the structure under temperature loads.
A further possible way of sealing off the circuit chamber is welding the housing to a stainless steel cover. This method is comparatively costly and the electrical connections have to be routed from the circuit carrier, through the stainless steel housing, to the outside, in particular via glass bushings. Faults in the process can easily occur in this case. Furthermore, gases which are produced in the interior of the housing by the welding process can be discharged again only with difficulty.